The development of intelligent transport systems has been progressing in recent years with the aim of supporting smooth automobile travel. For example, in the event of traffic congestion occurring in a particular road zone, a known system communicates the zone with traffic congestion to a vehicle on a road in the vicinity using road-to-vehicle communication or the like.
An example of such a system is described in Japanese Patent Application Publication No. JP-A-2003-288673, where a system monitors a fixed zone on a road using vehicle detection equipment, and determines a staying state of vehicles in each lane. If the staying of vehicles is detected in a left-turn lane in the vicinity of a facility, then the system determines that the vehicles are staying in the lane due to a large number of vehicles waiting to make a left turn, and communicates the congestion arising from the vehicles waiting to make a left turn to surrounding vehicles.
However, although the above system is capable of determining that vehicles are staying in the left-turn lane, the system cannot provide detailed information pertaining to a factor of such congestion. In other words, the system cannot determine whether the congestion has occurred because of staying vehicles waiting to park in a parking lot for the facility, or has occurred because of staying vehicles waiting to use a so-called drive-through.